Rupture of the left ventricular free wall is a major complication of acute myocardial infarction, and it usually leads to hemopericardium with tamponade. During the last 16 years, 138 patients with left ventricular free wall rupture during acute myocardial infarction have been studied in the Pathology Branch, NHLBI: 131 (95%) had associated hemopericardium with probable or definite tamponade, and 7 (5%) had no blood in the pericardial sac. The 7 patients without hemopericardium ranged in age from 46 to 93 years. The interval from onset of chest pain typical of myocardial infarction to death was 4 days or less in the 6 patients and 31 days in one patient. No previous reports have appeared describing complete left ventricular myocardial wall rupture without hemopericardium. All 7 patients had a great deal of subepicardial adipose tissue and the presence of that adipose tissue may have helped to prevent extravasation of blood into the pericardial space. Clinically, all 7 patients had features suggesting through and through rupture of both myocardium and epicardium with fatal hemopericardium.